Anorectal
melanoma

Anorectal melanoma is a rare cancer. It starts in the anus or rectum, or both. These are parts of the digestive system.

Symptoms can include:

bleeding from the back passage

pain, itching or a lump in the back passage

a change in your bowel habits

feeling the need to go to the toilet often.

It’s important to get these symptoms checked by your GP. They will examine you and do some tests.

If you are diagnosed with anorectal melanoma, you will have further tests to find out the size of the cancer and if it has spread. These tests help doctors to decide on the best treatment for you. The main treatment for anorectal melanoma is usually surgery. Sometimes other treatments are used to reduce the chance of the cancer coming back.

It’s natural to be feeling lots of different emotions. You may find it helps to talk about your worries with someone.

What is anorectal melanoma?

Anorectal melanoma is a rare cancer that starts in the anus or rectum (back passage), or both. The anus and rectum are parts of the digestive system. The rectum is the last section of the large bowel. The anus is the ring of muscle below the rectum. It controls when bowel motions leave your body.

Although melanoma is a cancer that usually starts in the skin, it can occasionally develop in other parts of the body. Melanoma develops from cells called melanocytes that give our skin its colour. Melanoma usually develops in the skin. But because there are melanocytes in different parts of the body, it can occasionally start in other areas, such as the lining of the anus or rectum.

Causes of anorectal melanoma

The cause of anorectal melanoma is not known. The main risk factor for developing skin melanoma is exposure to ultraviolet (UV) radiation from sunlight, sunbeds or sunlamps. But there doesn't seem to be any link between the risk factors for skin melanoma and anorectal melanoma.

How anorectal melanoma is diagnosed

You usually start by seeing your GP. They will feel your tummy (abdomen) and they may examine your back passage. This is called a rectal examination. To do this, your GP gently places a gloved finger into your back passage to feel for any lumps or swellings. If you find the examination painful, tell them.

If your GP isn’t sure what the problem is, or thinks your symptoms could be caused by cancer, they will refer you to a hospital specialist.

At the hospital, the specialist doctor will ask you about your symptoms and general health. They will also examine you. You will have another rectal examination. The doctor will also feel your groin to check whether any lymph nodes (sometimes called glands) are swollen. Women may also have an internal examination of their vagina.

You will then have some of the following tests.

Biopsy

This is when the doctor removes a small piece of tissue or cells. A pathologist (doctor who specialises in analysing cells) examines the tissue or cells under a microscope to look for cancer cells. A biopsy can be taken in different ways.

The doctor may put a thin tube called a proctoscope into your back passage to examine the anal canal and rectum. You’ll have this test in the hospital outpatients department or on a ward. You will be asked to lie curled on your left side while the doctor gently passes a tube into your back passage. The doctor can see any abnormal areas by using a tiny light and camera on the end of the tube. If needed, they can take a small biopsy. You should be able to go home as soon as the test is over.

This test can be uncomfortable or painful for some people. The doctor may arrange to examine the area more closely and take biopsies under an anaesthetic.

Further tests for anorectal melanoma

There are other tests that may be used to diagnose anorectal melanoma. These tests can also be used to check whether the cancer has spread. Several tests may be used.

CT (computerised tomography) scan

A CT (computerised tomography) scan uses x-rays to build a three-dimensional picture of the inside of the body. You may be given either a drink or injection of dye. This is to make certain areas of the body show up more clearly. This scan takes around 30 minutes and is painless. We have more detailed information about having a CT scan.

MRI (magnetic resonance imaging) scan

This scan uses magnetism to build up a detailed picture of areas of your body. You may be given an injection of dye, into a vein, to improve the images from the scan. This test is painless and will take around 30 minutes. We have more detailed information about having an MRI scan.

Anal ultrasound scan

This test uses soundwaves to build up a picture of the anus and rectum on a computer screen. For the ultrasound, you lie on your side while a nurse or doctor gently passes a small, lubricated probe into your back passage. The test takes about 30 minutes and is usually painless.

Fine needle aspiration (FNA) of the lymph nodes

You may have this test if the lymph nodes in your groin don’t feel normal or don’t look normal on a scan. An FNA checks whether there are any cancer cells in the lymph nodes.

The lymph nodes are part of your body’s system to protect you from infection and disease. Lymph nodes are small and bean-shaped. They filter out bacteria (germs) and disease.

The doctor passes a fine needle into the lymph node and withdraws (aspirates) some cells into a syringe. This might feel a little uncomfortable, but it’s very quick. You don’t usually need a local anaesthetic to numb the area. You might have a tummy (abdominal) ultrasound scan at the same time to help guide the needle.

After the test, a doctor will examine the sample under a microscope to check for cancer cells.

Staging for anorectal melanoma

The stage of a cancer describes its size and whether it has spread. Knowing the stage of the cancer helps the doctors decide on the best treatment for you.

There are different types of staging system used for different cancers. Because anorectal melanoma is rare, there isn’t a standard staging system used for it. However, your doctor might use a number staging system to describe the cancer.

There are usually three or four number stages:

Stage 1 describes early-stage cancer, when it is small and hasn’t spread.

Stage 4 describes cancer that has spread to other parts of the body.

Stage 2 and stage 3 are between these stages.

Your doctor might also use these words to describe a stage:

Early or local – if the cancer hasn't spread.

Regional or locally advanced – if it has begun to spread into surrounding tissues or nearby lymph nodes.

Treatment for anorectal melanoma

The main treatment for anorectal melanoma is usually surgery. Sometimes other treatments, such as radiotherapy and chemotherapy, are given to reduce the risk of the cancer coming back after surgery. Treatments are also given to manage the symptoms of cancer that has spread.

Your treatment plan will depend on the stage of the cancer and your general health. You and your doctor will decide on the best treatment plan for you.

Surgery

There are two types of operation used to treat anorectal melanoma. The aim is to remove all of the cancer, or as much of it as possible. The operation you have will depend on the stage of the cancer.

Local excision

During this operation, the surgeon removes the tumour and a small area (margin) of normal-looking tissue all around the tumour. This reduces the risk of cancer cells being left behind.

This is the most common operation for anorectal melanoma. Because the anal muscles aren’t usually damaged during surgery, you should still be able to control your bowel in the normal way after treatment.

Abdominoperineal (AP) excision

Some people need a bigger operation to remove the cancer. Your doctor may talk to you about an AP excision if:

you had a local excision but some cancer couldn’t be removed or has come back

the tumour is in a difficult area to remove with a local excision.

In an AP excision, the surgeon removes all of the anus and rectum. They may also remove nearby lymph nodes if the cancer has spread there. The surgeon closes the hole where the anus was. They make a cut on your tummy (abdomen) and join the end of your bowel to this opening. This is called a colostomy. After the operation, your bowel motions come through this opening (stoma) instead of your back passage. You wear a bag over the stoma to collect the bowel motions.

Being told you need a stoma is often frightening and distressing at first, but most people find they get used to it over time. You will get support and advice from a stoma nurse in your hospital. We have more information about living with a colostomy.

Sentinel lymph node biopsy

Your surgeon may talk to you about having a sentinel lymph node biopsy at the same time as your surgery. This test examines nearby lymph nodes for signs of cancer that might be too small to show up on a scan.

The surgeon injects a tiny amount of radioactive liquid and blue dye around the area of the tumour. Then they scan the closest lymph nodes to see which one gets the radioactive liquid and blue dye first. The surgeon removes this first lymph node (the sentinel node), to test it for cancer cells.

If the sentinel node doesn't contain cancer cells, it is less likely that the other lymph nodes in the area have been affected by the cancer. If the sentinel lymph node does contains cancer cells, the surgeon will usually remove other lymph nodes in the area.

Radiotherapy

Radiotherapy uses high-energy rays to destroy the cancer cells, while doing as little harm as possible to normal cells. You have treatment as a series of short, daily sessions (called fractions) over a few weeks. You have treatment from a machine similar to a large x-ray machine. Radiotherapy only treats the area of the body the rays are aimed at. It does not make you radioactive.

Radiotherapy may be given after surgery to reduce the risk of the cancer coming back. In this situation, the lymph nodes in the abdomen and groin can also be treated. Some people are given chemotherapy at the same time. This is called chemoradiation. Having both treatments together is more effective than having one of the treatments on its own. However, the side effects are also worse during chemoradiation. It is important that you are well enough to cope with having both treatments together.

Radiotherapy may also be given to control symptoms such as pain if the cancer has spread to other areas of the body. In this case you might only need a few days of treatment or even just a single dose.

Side effects of radiotherapy to the anorectal area

You may have side effects during your treatment. These usually disappear gradually over a few weeks or months after treatment finishes. Your radiotherapy team will let you know what to expect. Tell them about any side effects you have. There are often things that can help.

Radiotherapy to the anorectal area is likely to cause problems with your bowels, such as diarrhoea or passing more wind. Your doctor can prescribe drugs to help with this. Your nurse, radiographer or a dietitian may give you advice about changes to your diet that might help.

Your radiotherapy team will also give you advice about looking after your skin during treatment. It’s common to have a skin reaction in the area being treated. The skin around the anus and in the groin can become sore, red and may become blistered. This usually starts about 2–3 weeks after treatment starts. It may last for 3-4 weeks after treatment ends. Let your radiotherapy team know if your skin becomes sore. They may prescribe creams and painkillers to help.

Radiotherapy to the anorectal area can also irritate your bladder. You may feel as though you want to pass urine often and have a burning sensation when you pass urine. It helps to drink plenty of water and other fluids. Your doctor can prescribe medicine to make it more comfortable to pass urine.

Sometimes radiotherapy to the anorectal area causes long-term effects. These aren’t common, but they can happen months or even years after treatment. A small number of people find their bowel function is permanently changed.

Chemotherapy

You may have chemotherapy if surgery isn't possible or if the cancer comes back. You may have chemoradiation to reduce the risk of the cancer returning after surgery.

Side effects of chemotherapy

The side effects depend on the drug or combination of drugs you are given. Your doctor or nurse will explain any treatment you are offered and what to expect. During treatment, let them know about any side effects. They can often prescribe drugs to reduce these.

The most common chemotherapy drug used to treat anorectal melanoma is dacarbazine (also known as DTIC). This is usually given by injection into a vein (intravenously) once every three weeks for up to six doses.

Chemotherapy can reduce the number of white cells in your blood. During treatment, this will make you more likely to get an infection. Your doctor or nurse will advise you on what to do if this happens.

Chemotherapy can also make you feel sick (nausea) or possibly be sick (vomit). Your doctor will prescribe anti-sickness (anti-emetic) drugs to help control this.

Feeling very tired is another common side effect. It’s often worse towards the end of treatment and for some weeks after. Try to pace yourself and get as much rest as you need. It helps to balance this with taking some gentle exercise, such as short walks.

Some chemotherapy drugs can also make your mouth sore. Your nurse can give you more information about looking after your mouth during treatment.

If you find it hard to eat and drink because of any side effects, let your doctor or nurse know. They can give you advice and medications to help. They may refer you to a dietitian for more advice. You may need to take food supplements to add extra energy and protein to your diet. Some food supplements can be used to replace meals, and you take others in addition to your normal diet. A few of these food supplements are available directly from your chemist or the supermarket. But your doctor, nurse or dietitian can also prescribe them for you.

Targeted therapies

Targeted therapies are drugs that target the differences between cancer cells and normal cells. There are several targeted therapies used to treat melanoma. Some of these only work if the cancer has changes in genes called BRAF and c-KIT.

Your doctor may talk to you about this type of treatment if surgery isn't possible or if the cancer returns. This treatment may only be available if you take part in a clinical trial.

Clinical trials and new treatments

Cancer research trials are carried out to try to find new and better treatments for cancer. Trials that are carried out on patients are known as clinical trials.

Research into treatments for anorectal melanoma is ongoing and advances are being made. But because anorectal melanoma is rare, there may not always be a relevant trial in progress.

If there is a relevant trial in progress, you may be asked to take part. Your doctor will discuss the treatment with you so that you have a full understanding of the trial and what it means to take part. You may decide not to take part, or to withdraw from a trial at any stage. In this case, you'll still receive the best standard treatment available.

Follow-up for anorectal melanoma

After your treatment is completed, you will have regular check-ups and possibly scans or x-rays. You may continue to have these tests for several years. If you have any problems or notice any new symptoms between check-ups, let your doctor know as soon as possible.

Your feelings about anorectal melanoma

You may have many different emotions, from shock and disbelief to fear and anger. At times, these feelings can be overwhelming and hard to control. But they are natural and it's important to be able to express them.

Everyone has their own way of coping. Some people find it helps to talk to family or friends, while others get help from people outside their situation. Sometimes it’s helpful to share your experiences at a local cancer support group. Some people prefer to keep their feelings to themselves. There is no right or wrong way to cope, but help is available if you need it.

You may want to contact our cancer support specialists for more information and support. Our online community is also a good place to talk to people who may be in a similar situation.

Latest from the Online Community

Ask the experts

Read this recent webchat transcript, in which our Macmillan Support Nurses Anne and John answered questions on bowel, rectum and anal cancer. They suggested that someone affected by anal cancer should use a laxative in order to prevent constipation and to help with discomfort.

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